Plastic closure which can be produced in a closed manner, injection mould and method for the production thereof

ABSTRACT

A production of a plastic closure which is essentially a question of cost. Plastic closures with lower parts and covers that are joined to each other by a snap hinge can be manufactured in a particularly advantageous manner if the covers and lower parts are produced in a closed state. According to this invention, the closure is structured so that all the elements of the snap hinge are arranged in the covering wall areas of the closure, which extend in a parallel manner in relation to the direction of movement in which the injection mold is opened and closed. Thus, the cycle times are extremely short and the injection molds can be economically produced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a plastic closure including a lower part and acap and a snap hinge by which the two closure parts are connected to oneanother as one piece, wherein the lower part and the cap can bemanufactured in the closed state and also can be connected to oneanother via at least one separation seam. This invention also relates toan injection mold for manufacturing the plastic closures and to a methodwith which the above-mentioned closures may be manufactured using theinjection molds according to this invention.

2. Discussion of Related Art

Closures are known for example from Swiss Patent Reference CH-A-673,631.With this a plastic closure with a lower part may be placed on a bottleneck or onto an adapter fastened on the bottle neck. The snap effect ofthe closure is produced with a spring element which is a bending springthat projects from the container wall from the outside into the innerspace of the closure. Thus, the snap effect is not achieved by thedeformation of the container walls but solely by the restoring force ofthe U-shaped spring element.

Openings in the closure walls of the plastic closure are necessary formanufacturing the known plastic closures. On one hand an opening needsto be present in the outer, peripheral lateral wall or skirt in order toshape the U-shaped spring on the inner side, and on an other hand arecess needs to be in the cover surface in order to achieve the upper,outer surface of the U-shaped spring. The manufacture of such a closurethus necessitates relatively large mold slides or sliders which rendersthe injection molds considerably more expensive and also extends thecycle times. Accordingly, plastic closures of this known type arerelatively expensive and up to now could not assert themselves in themarketplace.

Finally, the lack of design freedom is a problem. The manufacturabilityspecifically requires a conical or step-like shaping of the plasticclosure, wherein the lateral walls of the cap with respect to the lowerpart need to be arranged offset to one another at least by the wallthickness.

The same concept as in Swiss Patent Reference CH-A-673,631 has also beentaught by Swiss Patent Reference CH-683,611. Here the plastic closurewhich is injected in the closed state is realized by arranging the lowerpart and the cap conically on top of one another. Here, in contrast tothe first mentioned design there is a snap hinge which is not achievedby a spring element designed as a bending spring, but by two flatintermediate elements through which the tensile forces are transmitted,wherein the spring force is realized solely by the deformation of theadjacent container walls. At the same time, it is necessary for thecontainer walls of the lower part and the cap to run inclined towardsthe center axis at least in the hinge region. Although such a closuremay be manufactured without a slider, it may not be used on conventionalbottle necks without an adapter. The necessary conicity results in adiameter difference between the lower part and the sealing peg in thecap which is larger than common bottle necks.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a plastic closure of thementioned type which requires only particularly simple injection molds,and which may be manufactured with short cycle times and that permits acylindrical shaping of the outer contour.

This object is achieved by a plastic closure as described in thisspecification and in the claims.

Another object of this invention is to manufacture an injection mold formanufacturing plastic closures of the above mentioned type, which areeconomical to manufacture and which may function with short cycle times.

An injection mold is also described in this specification and in theclaims.

This invention also relates to a method for manufacturing the closuresof the initially mentioned type while using the previously mentionedinjection mold, wherein the method has features and other design formsof this invention are explained in the subsequent description and in theclaims.

In one embodiment, the plastic closure according to this invention isrepresented in the accompanying drawing, whereby a representation of theinjection mold and a schematic representation of the method is not shownbecause the person skilled in the art would not require such arepresentation on account of the subsequent explanations.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of a plastic closure according to this invention is shownin the drawings wherein:

FIG. 1 is a lateral view of a plastic closure according to thisinvention, manufactured in a closed state, placed onto a partly showncontainer neck;

FIG. 2 shows the same view as FIG. 1 but after removal of a guaranteestrip;

FIG. 3 shows again the same plastic closure as shown in FIGS. 1 and 2but in a diametric vertical section in an opened condition; and

FIG. 4 shows a vertical section taken through the plastic closureaccording to FIG. 1, before opening for a first time, again shown placedonto a container neck.

DETAILED DESCRIPTION OF THE INVENTION

The plastic closure manufacturable in the closed state is shown in itsentirety as element 1 and comprises a lower part 2 and a cap 3. Thelower part 2 and the cap 3 are rotationally symmetrical with regard tothe center axis A. The lower part 2 comprises a lateral wall or skirt 5and the cap 3 comprises a lateral wall or skirt 6. The lower part 2 andthe cap 3 are connected to one another as one piece via a snap hinge 4.Furthermore, the lower part 2 and the cap 3 are connected to one anothervia at least one separation seam 7. At the same time the at least oneseparation seam 7 always runs from one side of the snap hinge 4circumferentially about the periphery of the plastic closure 1 to theother side of the snap hinge 4. The separation seam 7 may be formed by acontinuous separation line which is only interrupted by severaldestroyable bridges. In the preferred example shown, continuous thinlocations form a so-called tear seam.

The tear seams 8 in particular are clearly shown in FIG. 4, in which theclosure is shown in an enlarged scale. Here not a single tear seam 7 isshown but there are two tear seams 7 and 7′ running parallel to oneanother between which a guarantee strip 9 is present. The guaranteestrip 9 at least on one side near or in the vicinity of the snap hinge 4comprises a tear-open tab 10. In the normal case, the closure is notonly rotationally symmetrical with respect to the axis A, but thelateral walls 5, 6 represent sections of the same circular cylinder. Thelateral walls 5, 6 are thus situated vertically on top of one another ina completely flush manner. With this shaping the closure may also beused on standard bottle necks. Thus, the container B requires nospecially shaped bottle neck F. The cap 3 may have an annular sealingwall 10 which forms a sealing plug 11 that comes to lie directly intothe bottle neck F in a sealing manner without an adapter piece. Withthis not only are the manufacturing costs saved but also the assemblycosts.

The closure represented here may be pressed onto the container withconventional assembly machines without any problem and with a largecadence. In particular, with the use of continuous tear seam 8, therealso exists no danger that the fragile bridges are destroyed near or inthe region of the separation seam during assembly. The fastening of theclosure 1 on the container neck F is conventional and directlyintegrally formed on the lateral wall or skirt 5 of the lower part 2. Inthe example shown, this is an inwardly projecting peripheral retainingbead 12. Instead of the retaining bead 12 retaining bead sections can beprovided. In particular, in FIGS. 1 and 4, the lateral walls of theupper part and the lower part in the embodiment shown are completelysmooth on the outer surface. In contrast to this, the inner surfaces ofthe lateral walls of the upper part and lower part comprise inwardformations and outward formations. Inward formations and outwardformations are understood as changes in the wall thickness, whereinrecesses in the lateral wall or skirt surface are indicated as inwardformations which are considered here while outward formations areconsidered as protuberances with respect to the lateral wall or skirtsurface.

In the example shown here, all inward formations and outward formationsare arranged on the inner surface of the lateral walls of the lower partand lid. This is one sensible design but it is also possible toincorporate all inward formations and outward formations on the outersurfaces of the lower part and the lid. For achieving the objectaccording to this invention, it is necessary for the snap hinge to liein the lateral wall or skirt regions of the closure which run parallelto the closure and opening movement direction of the injection mold. Aninjection mold in the simplest case includes two tool halves. Thesetools are mostly also called plates. While the one tool half comprisescavities which form the outer surfaces of the closure manufacturedtherein, the other tool half comprises so-called mandrels which whentraversing together the two tool halves enter the cavities of the othertool half. The remaining cavity is filled with plastic and forms theplastic closure to be produced. While no shape deviations from thismovement direction were believed allowable, on the lateral walls whichrun parallel to the opening and closure movement without suitablesliders or other moving parts provided on the injection mold, now onehas moved away from this belief.

In particular, threads on closures or retaining beads are nowpermissible. It is essential that the two injection mold parts aretraversed apart, so that the material may escape at least on one side,in order to completely remove the respective injection mold object fromthe mold. The plastic closure according to this invention was conceivedin its design on the basis of this principle. In particular, with snaphinge closures, this manufacturing concept until now has not been usedfor producing the snap hinge. Particularly aesthetic closures resultfrom this concept if the lateral walls of the lower part 2 and the cap 3at least in the region of the snap hinge are arranged lying in a flushmanner on top of one another. With this, the region is understood as acylinder sector, and the regions of the snap hinge up to the coversurface 13 of the lid, and from the snap hinge 4 to the lower edge 14 ofthe lower part 2 lie on top of one another in a completely flush manner.The adjacent wall regions may be designed to run in an inclined manner.This however is not desirable in many cases. Accordingly, one wouldpreferably arrange the lateral walls 5, 6 lying on top of one another ina completely flush manner.

As mentioned, only the inner surfaces or only the outer surfaces shouldhave inward formations and/or outward formations. The inward formationsand/or outward formations may at the same time not exceed the wallthickness of the lateral walls. This is understood as within theframework of the usual accuracies and tolerances. The larger the totaldiameter of the closure, the larger the possible relative deviation.This is known to the person skilled in the art of plastics technology,and does not have to be explained any further.

One has freedom with regard to the shaping of the guarantee strip.However, the guarantee strip 9 and the tab 10 form part regions of thelateral walls 5, 6 which lie on top of one another. The closure may onlybe opened by tearing away the guarantee strip 9. As mentioned, andrepresented in the drawing, the separation seams 7, 7′ which delimit theguarantee strip run parallel to one another. If both separation seamsrun parallel to one another then they may run perpendicular or inclinedrelative to the center axis or to the central middle axis A of theclosure. Of course the separation seams 7, 7′ may also be arranged inplanes running differently to the central middle axis A, wherein in thespecial case the one separation seam may run perpendicularly to thecentral middle axis and the second separation seam 7 may run inclined tothe central middle axis A.

The snap hinge corresponds essentially to a snap hinge as known fromEuropean Patent Reference EP-A-0'056'469 or from U.S. Pat. No.3,135,456. These are snap hinges which are formed essentially of twofilm hinges. The one film hinge 41 represents the movable connectionbetween the lateral wall or skirt 6 of the cap 3 and an intermediateelement 43, the second film hinge 42 forms the separation line betweenthe lateral wall or skirt 5 of the lower part 2 and the intermediateelement 43 of the snap hinge 4. The snap hinge has lateral limitations44 which are formed by a gap. The film hinges 41, 42 between the twolateral limitations 44 may have various running directions. Thus, thepreviously mentioned documents are incorporated by reference. Basically,the film hinges 41, 42 may centrally approach one another or run partbetween the two limitations 44. Furthermore, the film hinges may have anarcuate shape, or one which is sharply bent, and they may approach oneanother to such an extent that they mutually contact, by which twolateral intermediate elements 45 transmitting tensile forces arise. Asmentioned, the lateral limitations 44 are separated from the lateralwalls 5, 6 by a gap. This gap 46 thus forms the separation between theintermediate element or the intermediate elements or between theelements and the adjacent lateral walls 5, 6. However, the laterallimitations 44 may however also be connected to the adjacent lateralwalls practically as an additional guarantee element, wherein theconnections need to be designed as separation seams. When opening theclosure for the first time, these separation seams would tear.

As mentioned, the plastic closures according to this invention may bemanufactured by injection molds, wherein an injection mold includes twoplates of which the one plate comprises the cores and the other platethe cavities. At the same time, at least one of the two plates has norecesses or protuberances on the surfaces parallel to the extensiondirection of the plate. Accordingly, plastic closures which aremanufactured by these injection molds have no inward formations oroutward formations on the corresponding lateral wall or skirt surfaces.For the manufacture of the closures as are represented in the FIGS. 1 to4, the plate with the mandrels with the surfaces parallel to theextension direction have protuberances and/or recesses which form thecorresponding outward formations and/or inward formations, while thecavities on the other plate on the surfaces lying parallel to theextension direction have no recesses or protuberances. A correspondingreversion is likewise possible.

If one operates with the described injection molds in order to shape thecorresponding closures, it is necessary to extend that plate which hasno recesses or protuberances on the surfaces running parallel to theextension direction. If then the closures are set free on one side, thenthey may be ejected under suitable elastic deformation from the otherplate on which corresponding recesses or protuberances are parallel tothe extension and retraction direction of the molds. Usually, with this,as already mentioned, one would shape the cavities free of recesses andprotuberances. Accordingly, first the plate comprising the cavities isretracted and after this the cores are pulled from the closures. Again,a reversion is also possible. If the closures have smooth inner surfacesof the lateral walls, one may then first pull the cores from theclosures and of course after this eject the closures from the cavities.

1. A plastic closure comprising: a lower part, a cap and a snap hingeconnecting the lower part and the cap to one another as one piece, thelower part and the cap manufacturable in a closed state and connected toone another by at least one separation seam, and all elements of thesnap hinge positioned in a lateral wall region of the closure which runparallel to a closing and opening movement direction of an injectionmold.
 2. A plastic closure according to claim 1, wherein the lateralwalls of the lower part and the cap are arranged on top of one anotherin a flush manner at least in a region of the snap hinge.
 3. A plasticclosure according to claim 1, wherein the lateral walls of the lowerpart and the cap lie on top of one another in a completely flush manner.4. A plastic closure according to claim 3, wherein the lateral walls ofthe lower part and the cap on an outer surface are free of one of inwardformations and outward formations, and inner surfaces comprise at leastone of inward formations and outward formations not exceeding a wallthickness of the lateral walls.
 5. A plastic closure according to claim3, wherein the lateral walls of the lower part and the cap on the innersurface are free of one of inward formations and outward formations, andthe outer surfaces have at least one of inward formations and outwardformations not exceeding a wall thickness of the lateral walls.
 6. Aplastic closure according to claim 1, wherein the lower part and the capare connected to one another by two separation seams which delimit aguarantee strip, and the two separation seams proceeding from a laterallimitation of the snap hinge are positioned around the closure up to atleast approximately an other lateral limitation of the snap hinge.
 7. Aplastic closure according to claim 6, wherein the two separation seamsrun parallel to one another.
 8. A plastic closure according to claim 6,wherein the two separation seams run in two planes perpendicular to acentral middle axis of the closure.
 9. A plastic closure according toclaim 6, wherein the two separation seams run in planes inclined to acentral middle axis of the closure.
 10. A plastic closure according toclaim 6, wherein the two separation seams run in planes which aredifferently inclined with respect to a central middle axis of theclosure.
 11. A plastic closure according to claim 1, wherein the snaphinge is formed of two film hinges which from one lateral limitation toan other limitation of the snap hinge follow a course that one ofcentrally approach one another and diverge from one another.
 12. Aplastic closure according to claim 11, in that wherein the two filmhinges at a middle portion contact one another at least approximatelyand follow one of a curved course and a sharp bend, wherein Hey the filmhinges laterally enclose two lateral intermediate elements transmittingtensile forces.
 13. A plastic closure according to claim 11, wherein thelateral limitations of intermediate elements are separated from thelateral walls by a gap.
 14. A plastic closure according to claim 11,wherein the lateral limitations of intermediate elements are connectedto the adjacent lateral walls by separation seams that tear on openingfor a first time.
 15. A plastic closure according to claim 14, whereinan injection mold for manufacturing the plastic closure has two plates,one of the plates has cores and an other of the plates has cavities, andat least one of the plates on surfaces parallel to an extensiondirection of the plates is free of one of recesses and protuberances.16. An injection mold according to claim 15, wherein mandrels on the oneplate in the surfaces parallel to the extension direction comprise atleast one of protuberances and recesses, and the other plate with thecavities on surfaces parallel to the extension direction is free of oneof recesses and protuberances.
 17. An injection mold according to claim15, wherein the cavities in the surfaces parallel to the extensiondirection are one of recesses and protuberances, and the surfaces ofmandrels parallel to the extension direction are free of one ofprotuberances and recesses.
 18. A plastic closure according to claim 17,wherein a method for manufacturing the plastic closure comprises firstextending the plates with one of the mandrels and the cavities withsurfaces parallel to the extension direction which are free of one ofthe recesses and the protuberances and then ejecting the plasticclosures which are free at one side from the other plate.
 19. A methodaccording to claim 18, wherein first the other plate with the cavitiesis retracted and then cores are pulled from the plastic closures.
 20. Amethod according to claim 18, wherein first cores are pulled from theplastic closures and then the plastic closures are ejected.
 21. Aplastic closure according to claim 15, wherein a method formanufacturing the plastic closure comprises first extending the plateswith one of mandrels and the cavities with surfaces parallel to theextension direction which are free of one of the recesses and theprotuberances, and then ejecting the plastic closures which are free atone side from the other plate.
 22. A method according to claim 21,wherein first the other plate with the cavities is retracted and thencores are pulled from the plastic closures.
 23. A method according toclaim 21, wherein first cores are pulled from the plastic closures andthen the plastic closures are ejected.
 24. A plastic closure accordingto claim 1, wherein an injection mold for manufacturing the plasticclosure has two plates, one of the plates has cores and an other of theplates has cavities, and at least one of the plates on surfaces parallelto an extension direction of the plates is free of one of recesses andprotuberances.
 25. An injection mold according to claim 24, whereinmandrels on the one plate in the surfaces parallel to the extensiondirection comprise at least one of protuberances and recesses, and theother plate with the cavities on surfaces parallel to the extensiondirection is free of one of recesses and protuberances.
 26. An injectionmold according to claim 24, wherein the cavities in the surfacesparallel to the extension direction are one of recesses andprotuberances, and the surfaces of mandrels parallel to the extensiondirection are free of one of protuberances and recesses.